Device for supplying thermal energy to one or more places to be heated

ABSTRACT

A device for supplying thermal energy to a place to be heated, comprising a combustion chamber constructed from a number of slit-like flow ducts for reacting air-fuel mixture, which ducts immediately adjoin, with their inlet side, the inlets for air of combustion and fuel. The ducts are bounded mainly by parts of a heat-transmitting wall through which thermal energy can be withdrawn from the reacting air-fuel mixture.

Michels et al.

' Mar. 6, 1970 DEVICE FOR SUPPLYING THERMAL ENERGY TO ONE OR MORE PLACES TO BE HEATED U.S. Philips Corporation, New York, NY.

Filed: Feb. 8, 1971 Appl. No.: 113,520

Assignee:

Foreign Application Priority Data Netherlands 7003199 U.S. Cl. ..126/110 R, 126/116 R, 165/16 S Int. Cl. F28d 7/00 Field of Search 126/110 R, 91 A, 116 R;

References Cited UNITED STATES PATENTS McIntosh 237/16 [451 Get. 22, 1974 2,225,023 12/1940 Watt 237/17 2,879,762 3/1959 Robson 126/110 R 2,884,048 4/1959 Marble et al 126/110 R 3,056,398 10/1962 Kirk 126/110 R 3,073,583 1/1963 Woollen, Jr 432/223 3,134,582 5/1964 Robson 432/223 3,258,004 6/1966 Bedell et al. 126/110 R 3,315,655 4/1967 Stone et al 126/91 A 3,468,300 9/1969 Geyer et a1 165/105 X 3,610,330 10/1971 Nasser 165/166 Primary ExaminerJohn J. Camby Assistant Examiner-W. E. Tapolcai, Jr. Attorney, Agent, or FirmFrank R. Trifari 5 7 ABSTRACT A device for supplying thermal energy to a place to be heated, comprising a combustion chamber constructed from a number of slit-like flow ducts for reacting air-fuel mixture, which ducts immediately ad join, with their inlet side, the inlets for air of combustion and fuel. The ducts are bounded mainly by parts of a heat-transmitting wall through which thermal energy can be withdrawn from the reacting air-fuel mixture.

3 Claims, 15 Drawing Figures PAIENIEBnm-zzm I sum 1 w s Fig.1b

INVEN'IOR ALBERTUS P.J. MICHELS S ROELF J. MEIJER HENRICUS C.J. VAN BEUKERING A EH71 7* PAIiNIED ZZ 3.842. 20

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I N VENTORS ALBERTUS P.J. MICHELS ROELF J. ME JER HENRICUS C.J. VAN BEUKERING DEVICE FOR SUPPLYING THERMAL ENERGY TO ONE OR MORE PLACES TO BE HEATED The invention relates to a device for supplying thermal energy to one or more places to be heated, comprising a combustion chamber with which communicate at least one inlet for air of combustion and at least one inlet for fuel.

Devices .of this type are known and are used in various places, for example, in hot-gas engines in which a working medium performs a closed thermodynamic cycle, such as hot-gas reciprocating engines and hot-gas turbines, to supply thermal energy to the heater of said engines.

In the known devices, the hot gases of combustion formed in the combustion chamber are conducted to the place to be heated, deliver thermal energy there, and are then exhaused to the atmosphere, if desirable after first having exchanged heat with, for example, air of combustion to be supplied to the combustion chamher.

It has been found that the gases of combustion removed from the device contain a certain quantity of nitrogen oxides. These nitrogen oxides are detrimental to health and may therefore not exceed a certain concentration in the atmosphere. All this makes the device less suitable for use in places where air pollution is to be minimized. Such places are, for example, factory spaces and storage spaces, mines and the like, in which the device can be arranged stationary or form part, for example, of the heating system of hot-gas engines for traction purposes. Such places should then be ventilated which of course is disadvantageous.

In cities with their large population concentration and traffic densities, such devices as an integral part of the energy source in vehicles are also less suitable owing to the exhausted nitrogen oxides.

It is the object of the invention to provide a device for supplying energy in which the quantity of nitrogen oxides present in the gases of combustion is considerably smaller than in the known devices.

The present invention is based on the recognition of the fact that the formation of-nitrogen oxides increases strongly with the temperature at which the combustion takes place and on the recognition of the fact that the combustion process in the combustion chamber occurs substantially adiabatically. Decrease of the quantity of nitrogen oxides in the gases of combustion on be obtained according to the invention by ensuring that the temperature at which combustion takes place in the combustion chamber does not rise too high.

In order to realize the end in view, the device according to the invention is characterized in that the combustion chamber is constructed from a number of slit-like flow ducts for reacting air-fuel mixture which ducts immediately adjoin, with their inlet side, the inlets for fuel and air of combustion, said ducts being mainly bounded by parts of at least one heat transmitting wall through which heat can be withdrawn from the reacting air-fuel mixture. By withdrawing thermal energy from the air-fuel mixture while this mixture reacts the adiabation of the combustion process is disturbed and the chemical reactions occur at lower temperature. At the low temperature level in the combustion chamber, less formation of nitrogen oxides occurs so that the gases of combustion removed from the device contain fewer nitrogen oxides.

Owing to the slit-like flow ducts there is an intimate thermal contact between the reacting mixture and the heat transmitting wall so that there is no danger of the reaction temperatures increasing strongly locally, with the evil result of strong formation of nitrogen oxides at the area.

Since furthermore, the slit-like duets with their inlet side adjoin immediately the inlets for air and fuel, it is prevented that the air-fuel mixture in the combustion chamber reacts outside the ducts where strong formation of nitrogen oxides could also take place due to considerably increasing reaction temperatures.

It is possible to collectively supply the total quantity of fuel and the total quantity of air of combustion to the inlet side of the slit-like ducts.

In a favourable embodiment of the device according to the invention, however, a number of inlets for fuel or air of combustion which viewed in the direction of .flow are arranged one behind the other after the inlet side communicate with the flow inlets. By supplying only a part of the totally required quantity of fuel and air of combustion, respectively, to the inelt side of the flow ducts and supplying the remainder of said fuel and air of combustion, respectively, to a number of places of the flow ducts which are situated downflow, the following advantages are obtained. It is ensured that the chemical reactions do not occur mainly in the proximity of the inlet side of the slit-like duct in said ducts but distributed over the whole dimensions of said ducts. All the wall parts of the heat-transmitting wall(s) then contribute to the same extent to the removal of thermal energy. This means on the one hand that in the proximity of the inlet side there is no danger of strong formation of nitrogen oxides and of thermal overload of the heat transmitting wall(s) as a result of too high reaction temperatures. On the other hand, the whole available surface of the heat-transmitting wall(s) is efficiently used for withdrawing thermal energy from the reacting mixture, so that a homogeneous temperature distribution is adjusted over the said surface which is favourable for an efficient heat transfer to cooling medium which is present on the side of the heat transmitting wall remote from the flow ducts, as well as for avoiding thermal stresses in the heat transmitting wall.

Of course it should be ensured that during operation of the device the temperature of the heat-transmitting wall(s) remains sufficiently high to ensure in all circumstances the complete combustion of the reacting air-fuel mixture in the flow ducts.

In a further favorable embodiment of the device according to the invention, the side of the heat transmitting wall remote from the flow ducts also forms the boundary of a heat-transporting device in which aheattransporting medium is present which can withdraw thermal energy from the reacting air-fuel mixture through the heat transmitting wall and can deliver thermal energy elsewhere to a place to be heated via a further heat transmitting wall. In this manner, the thermal energy withdrawn from the reacting mixture can be rapidly and efficiently be conveyed with simple means to a place to be heated and be delivered there.

According to a further favorable embodiment of the device according to the invention, the heattransporting device is constituted by a closed space and the heat-transporting medium withdraws thermal energy from the reacting air-fuel mixture while being converted from the liquid phase into the vapour phase, and

supplies thermal energy to the place to be heated while being converted from the vapour phase into the liquid phase. By using an evaporation-condensation system it is possible to withdraw per unit of time a large quantity of thermal energy from the reacting mixture and to transport it to the place to be heated. The use of a liquid ensures a good heat transfer between the heat transmitting wall and liquid, while owing to the comparatively high evaporation heat, a large quantity of thermal energy can be stored in the vapor. In addition, the thermal transport takes place without noteworthy temperature loss. Therefore such a device is extremely suitable, for examle, for supplying thermal energy to the heater of hot-gas engines and hotgas turbines having a closed thermodynamic cycle. Hot-gas engines, as

compared with internal combustion engines, inter alia have the advantage that the gases of combustion-are considerably cleaner, i.e. contain fewer carbon monoxides and unburnt hydrocarbons. By providing the hotgas engine with the device described, an engine is obtained in which the quantity of nitrogen oxides in the exhaust gases is also extremely small which consequently makes this engine particularly suitable for use in places where air-pollution should be minimized. In addition, the advantage of a very favourable heat transfer is obtained in the present case.

Whereas in the known hot-gas engine a system of heater pipes of comparatively large dimensions is necessary to achieve that the gases of combustion can deliver their thermal energy to the working medium in the engine, it is sufficient for the present device to use, in much more favourable heat transfer conditions, a small and simple evaporation-condensation system, and a ditto heater. As in the known hot-gas engine, the remaining thermal energy in the gases of combustion which leave the combustion chamber can furthermore be used to preheat air of combustion.

When the further heat-transmitting wall of the closed space serving as a condensation wall lies at a higher level than the heat-transmitting wall serving as an evaporation wall, the return of condensate to the heattransmitting wall can take place under the influence of gravity. Such an arrangement, however, will not always be possible or desirable.

For that purpose, a further favorable embodiment of the device according to the invention is characterized in that a porous mass present in the closed space communicates the heat-transmitting wall and the further heat transmitting wall together. As a result of the capillary action of the said porous mass, the return of condensate can now also take place without the support of gravity and even against gravity. All this means a great independence of position and hence freedom in arrangement of the device.

In a further favorable embodiment of the device according to the invention the heat-transporting device is constituted by a closed system of ducts in which the heat-transporting medium can circulate by means of a pumping device incorporated in the said system.

The invention furthermore relates to a hot-gas engine, for example, a hot-gas reciprocating engine or a hot-gas turbine, in which a gaseous working medium traverses a closed thermodynamic cycle and to which working medium thermal energy is supplied from without through the wall of a heater. The hot-gas engine according to the invention is characterized in that it comprises a device for supplying thermal energy to one or more places, which device has been described above.

As already described, such a hot-gas engine presents the great advantage that the gases of combustion originating from such engines, are substantially free from not only detrimental carbon monoxides and unburnt hydrocarbons, but also from detrimental nitrogen oxides. As a result of this an engine is obtained which is extremely suitable for use in those places where air pollution should be minimized. In addition, such an engine can be compact of construction by using a device for supplying thermal energy in which the heat transmitting wall forms part of an evaporation-condensation system which communicates with the heater of the engine.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which few embodiments are shown diagrammatically and not to scale.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 show devices for supplying thermal energy to one or more places.

FIGS. 3 and 4 show devices for supplying thermal energy in which the heat transmitting wall also forms part of a heat-transporting device constructed as a closed evaporation-condensation system.

FIGS. 5 and 6 show hot-gas engines, the heaters of which communicate with a device for supplying thermal energy via a closed evaporation-condensation system.

FIG. 7 shows a device for supplying thermal energy in which the heat transmitting wall also forms part of a heat transporting device constructed as a closed system of ducts in which heat-transporting medium can circulate.

FIG. 1a shows a device for supplying thermal energy.

FIG. 1b is a cross-sectional view of the device taken on the line IbIb of FIG. 1a, while FIG. 10 is an elevation of FIG. la in the direction of the arrow A.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1 denotes a combustion chamber with which an inlet 2 for air of combustion, an inlet 3 for fuel, and an outlet 4 for gases of combustion communicate. The combustion chamber is constructed from a number of slit-like combustion ducts 5, which are mainly bounded by a heat transmitting wall 6 which in this case has a pleaded construction. The further boundaries are side surfaces 7, lower surface 8, and upper surface 9 these ducts are shown to be generally planar, with a planar space between each two ducts.

The inlet side 10 of the slit-like ducts immediately adjoints the inlets 2 and 3.

The operation of the device is as follows: air of combustion and fuel is supplied to the slit-like ducts 5 via the inlets 2 and 3, the air-fuel mixture reacting in said ducts. While the chemical reaction take place, thermal energy is withdrawn from the reacting mixture in the slit-like ducts 5 through the heat transmitting wall 6 by conducting a cooling medium along the outside of the heat transmitting wall 6 in similar secondary ducts. As a result of this, the reaction temperatures do not rise high, so that the formation of nitrogen oxides substantially does not occur. Since the slit-like ducts immediately adjoin the inlets, air-fuel mixture cannot react elsewhere, that is to say, outside said ducts, and produce there high reaction temperatures with consequent strong formation of nitrogen oxides. Since furthermore the ducts are constructed in the form of slits, an intimate thermal contact between reacting mixture and the heat transmitting wall is ensured while in addition a large heat transmitting surface of the said wall is available, a slit being generally defined as a long narrow opening, where the length is substantially greater than the width, resulting in a relatively large circumference of a slit in cross-section for a given area of the crosssection.

The gases of combustion formed in the ducts leave the combustion chamber 1 via the outlet 4.

The device shown in FIG. 2 in general is the same as that shown in FIG. 1. Therefore the same reference numerals are used for corresponding components. FIG. 2b is a' cross-sectional view taken on the line IIbIIb of FIG. 2a; FIG. again is an elevation of FIG. 2a in the direction of the arrow A.

The device furthermore comprises a number of inlets 11 which, viewed in the direction of flow, are situated one behind the other and communicate with the flow ducts 5.

By supplying only a part of the air of combustion (or fuel) to inlet 2 (inlet 3) and supplying the remainder to the inlet 11, it is ensured that mixture reacts at any place in the slit-like ducts 5 and the whole heat transmitting wall 6 is used to withdraw thermal energy from the reacting mixture. This provides a uniform temperature of the reacting mixture in the combustion chamber which is favourable for inhibiting the formation of nitrogen oxides. The heat transmitting wall will also assume a uniform temperature and therefore be thermally loaded everywhere to the same extent. I

In the device shown in FIGS. 3a and 3b, the heat transmitting wall 6 also forms a wall of a closed space 12, in which a heat-transporting medium is present which can withdraw heat from the reacting mixture through the heat transmitting wall 6 while being converted from the liquid phase into the vapor phase and can deliver thermal energy, via a further heat transmitting wall of the space 12, to a place to be heated while being converted from the vapor phase into the liquid phase. For the rest the operation of the device is the same as that of the device of FIG. 1. With this device a large quantity of thermal energy can rapidly and efficiently be withdrawn from the reacting air-fuel mixture, transported and delivered to a place to be heated. The choice of the heat-transporting medium is determined, for example by the desirable operating temperature of the heat transmitting wall at which complete combustion still takes place in the combustion ducts.

FIG. 4 shows the device for supplying thermal energy according to FIG. 2, in which the heat transmitting wall 6 forms a wall of one (FIG. 4b) or more (FIG. 4c) closed spaces 12, in which, as in the device shown in FIG. 3, a heat-transporting medium is present which withdraws thermal energy from the reacting air-fuel mixture through the heat transmitting wall 6 while being converted from the liquid phase into the vapor phase and can supply thermal energy to one or more places to be heated, through the further heat transmitting wall 13 while being converted from the vapor phase into the liquid phase.

A porous mass 14 is provided on the inner walls of the closed spaces 12. This porous mass has such a capillary structure that, while using the surface tension of liquid heat-transporting medium in the given operating position of the space 12, it is capable, by capillary action, of returning condensate formed on the further heat transmitting wall 13 to the heat transmitting wall 6. In this manner the return of condensate is possible without using gravity, or, in the absence of gravity, even against gravity. This provides a great freedom in the arrangement of the device.

The porous mass may be constituted, for example, by ceramic materials, by wire or ribbon-shaped material of metals or metal alloys, or by an arrangement of pipes. A system of grooves in the inner wall of the space, whether or not in combination with one of the other above-mentioned alternatives, is also among the possibilities.

FIG. 5 shows a hot-gas engine provided with a device for supplying thermal energy shown in FIG. 3. Reference numeral M denotes the cylinder of a hot-gas engine, namely that part in which during operation the working medium is always at a high temperature. Inside the cylinder is a displacer 15 which, by an upward movement via a driving mechanism (not shown) connected to the displacer rod 16, can move warm working medium from the expansion space 17 to the cold side of the engine. The working medium flows through a heater 18, a regenerator 19 and a cooler 20. Thermal energy can be supplied from without to the working medium in the expansion space 17 through the wall of the heater 18. The wall of the heater 18 forms the further heat transmitting wall 13 of the closed space 12.

During operation, thermal energy is withdrawn from reacting air-fuel mixture in the device ll through the heat-transmitting wall6 by the liquid-transporting medium which is present inside space 12 on the said wall. This transporting medium evaporates and moves towards the further heat transmitting wall 13 as a result of the comparatively low vapor pressure prevailing there owing to the slightly lower temperature at that area. The vapor then condenses on the further heat transmitting wall 13 while giving off the heat of evaporation to the said wall. Under the influence of gravity the condensate flows back to the heat transmitting wall 6 to be evaporated again there.

The heat of evaporation which is released by condensation of transporting medium on the further heat transmitting wall 13 flows through said wall to the working medium in the expansion space 17 to compensate for the calorific energy converted during the expansion of the working medium into mechanical energy and to also compensate for the normal calorific losses.

As transporting media in the space 12 for the high temperatures (approximately 700 C) of the heater occurring in the hot-gas engine are to be considered, for example, the metals sodium, potassium, lithium, cadmium, cesium, metal salts, such as the metal halogens zinc chloride, aluminium bromide, cadmium iodide, calcium iodide, zinc bromide or mixtures thereof. To be considered are furthermore nitrates, nitrites or mixtures thereof.

FIG. 6 shows a hot-gas engine which comprises a device for supplying thermal energy as is shown in FIGS. 4a and 4b, namely in a cross-sectional view (FIG. 6a)

and in a cross-sectional view taken on the line Vlb Vlb (FIG. 6b) of FIG. 6a.

For corresponding components as in the FIGS. 4 and 5, the same reference numerals are used. By means of a controllable fan 21, air of combustion can be sucked in which is supplied to inlet 2 and inlets ll, respectively, via a heat exchanger 22, a duct 23, a distribution cock 24 and ducts 25 and 26. The supply of fuel takes place via inlet 3. Gases of combustion which leave the combustion chamber via outlet 4 are supplied, via a duct 27, to heat exchanger 22 in which they supply their remaining thermal energy to air of combustion which consequently enters the combustion chamber in a preheated condition. The operation of the device in general is the same as that of the device shown in FIG. 5. It is distinguished essentially only from that shown in FIG. 5 by the presence of the porous mass 14 which, by capillary action, is capable of returning condensate formed on the further heat transmitting wall 13 to the heat transmitting wall 6 without using gravity. This provides a great freedom in the arrangement of the hot-gas engine.

Owing to the clean exhaust gases, said hot-gas engine is very suitable for use in those places where the pollution of the atmosphere should be drastically restricted. The combustion chamber constructed from the slit-like flow ducts together with the evaporation-condensation system forms a compact heating system with good heat transfer properties and also enables the hot-gas engine in its totality to be constructed in a compact form.

Such a compact heating system is also extremely suitable for supplying thermal energy to the heater of a hot-gas engine comprising said compact system in a manner different from the withdrawal of thermal energy from mixture reacting in the slit-like flow ducts, namely by withdrawing thermal energy in the said ducts from gases heated elsewhere.

In the device shown in FIG. 7 the heat transmitting wall 6 also forms the boundary of a closed system of ducts 28, in which a heat-transporting medium is present which can circulate in said system of ducts by means of a pumping device 29.

Thermal energy withdrawn from the reacting medium by the heat-transporting medium via heattransmitting wall 6 is supplied in a heat exchanger 30 to a place to be heated. Heat-transporting medium which has supplied thermal energy in the heat exchanger 30, is again conveyed along the heattransmitting wall 6 by the pumping device 29.

What is claimed is:

1. Apparatus operable with a source of air and fuel to produce thermal energy to be transferred to a medium, comprising a combination combustion and heating chamber including an inlet for said air, and an inlet for said fuel, and an outlet, the chamber having walls which define a plurality of combustion ducts in which said air and fuel are mixed and in which combustion of said mixture and production of said thermal energy occurs, said combustion ducts having width substantially greater than height, with similar secondary ducts defined between each two combustion ducts and with said medium contained in said secondary ducts, and at least one wall of each of said combustion ducts being a boundary wall through which said thermal energy is transferred outward to said medium in the secondary ducts.

2. Apparatus according to claim 1 further comprising a second chamber having walls which define a closed space with a first of said walls being one of said boundary walls of said combustion ducts, and a second of said walls being heattransmitting and spaced from said first, and said medium which is a heat-transporting fluid situated within said second chamber, said fluid being cyclically changeable between liquid and vapor physical states, whereby thermal energy is transferred through said first wall and absorbed by the fluid in a liquid state which is changed to its vapor state and moves to said second wall which absorbs thermal energy from the vapor which returns to its liquid state and flows back to said first wall.

3. Apparatus operable with a source of air and fuel for burning said air and fuel to produce thermal energy comprising, a combination combustion and heating chamber including an inlet for said air and an inlet for said fuel and an outlet, the chamber having walls which define a plurality of combustion ducts which have width substantially greater than height with similar secondary ducts defined between each two combination ducts, and in which said air and fuel are mixed and in which combustion of said mixture and production of said thermal energy occur, at least one wall of each of said combustion ducts being a boundary wall through which said thermal energy is transferrable, the apparatus further comprising means for withdrawing thermal energy from said combustion ducts by transferring said energy through said boundary walls to reduce the temperature of said combustion, and thereby reduce the formation of nitrogen oxides. 

1. Apparatus operable with a source of air and fuel to produce thermal energy to be transferred to a medium, comprising a combination combustion and heating chamber including an inlet for said air, and an inlet for said fuel, and an outlet, the chamber having walls which define a plurality of combustion ducts in which said air and fuel are mixed and in which combustion of said mixture and production of said thermal energy occurs, said combustion ducts having width substantially greater than height, with similar secondary ducts defined between each two combustion ducts and with said medium contained in said secondary ducts, and at least one wall of each of said combustion ducts being a boundary wall through which said thermal energy is transferred outward to said medium in the secondary ducts.
 2. Apparatus according to claim 1 further comprising a second chamber having walls which define a closed space with a first of said walls being one of said boundary walls of said combustion ducts, and a second of said walls being heattransmitting and spaced from said first, and said medium which is a heat-transporting fluid situated within said second chamber, said fluid being cyclically changeable between liquid and vapor physical states, whereby thermal energy is transferred through said first wall and absorbed by the fluid in a liquid state which is changed to its vapor state and moves to said second wall which absorbs thermal energy from the vapor which returns to its liquid state and flows back to said first wall.
 3. Apparatus operable with a source of air and fuel for burning said air and fuel to produce thermal energy comprising, a combination combustion and heating chamber including an inlet for said air and an inlet for said fuel and an outlet, the chamber having walls which define a plurality of combustion ducts which have width substantially greater than height with similar secondary ducts defined between each two combination ducts, and in which said air and fuel are mixed and in which combustion of said mixture and production of said thermal energy occur, at least one wall of each of said combustion ducts being a boundary wall through which said thermal energy is transferrable, the apparatus further comprising means for withdrawing thermal energy from said combustion ducts by transferring said energy through said boundary walls to reduce the temperature of said combustion, and thereby reduce the formation of nitrogen oxides. 